topic Re: LPC43xx windowed watchdog timer reset flag in LPC Microcontrollers

LPC43xx windowed watchdog timer reset flag

lpcware — Wed, 15 Jun 2016 18:37:06 GMT

Content originally posted in LPCWare by wlamers on Fri Jul 18 05:49:50 MST 2014
I have a system that needs reset when an initialisation error occurs. Unfortunately setting bit 0 of RESET_CTRL0 of the reset generation unit (RGU) does not work as I would expect. The core seems to reset (indicated by the LED's all burning) but then it is stuck somewhere as if the wrong address is loaded or something.

Therefore I use the WWDT to force a reset. This actually works as expected. The only thing I need is to check what caused the reset (after a boot/reset). There is a flag in the MOD register of the WWDT called WDTOF (bit2). In contrast to what the manual states, this bit stays 0 after a WWDT reset. I tried setting it by hand (to 1) before starting the WWDT causing the reset. But even than is the flag 0 after the reset. Hence I can not check if the WWDT caused the reset. I tried this on two boards but both behave the same.

What am I doing wrong here?

Re: LPC43xx windowed watchdog timer reset flag

lpcware — Wed, 15 Jun 2016 18:37:07 GMT

Content originally posted in LPCWare by wlamers on Mon Jul 21 11:32:24 MST 2014
Nobody has run into this before?

Re: LPC43xx windowed watchdog timer reset flag

lpcware — Wed, 15 Jun 2016 18:37:08 GMT

Content originally posted in LPCWare by DF9DQ on Fri Jul 25 12:52:09 MST 2014
The problem is that a watchdog reset triggers a core reset, which then resets the watchdog peripheral itself, deleting any sign of a watchdog reset.

You can use indicators in the event router instead, not without another trick... But the attached example shows what you need to do. See the comments in main.c

Re: LPC43xx windowed watchdog timer reset flag

lpcware — Wed, 15 Jun 2016 18:37:08 GMT

Content originally posted in LPCWare by wlamers on Mon Jul 28 06:01:25 MST 2014

Quote: DF9DQ
The problem is that a watchdog reset triggers a core reset, which then resets the watchdog peripheral itself, deleting any sign of a watchdog reset.

That explains a lot. Not a very useful flag in that case, so to say.

Thank you for your example. I had solved the issue using a suggestion from the manual is section 14.5.1 by setting a, non-initialised, variable that is given a magic number after successful boot and (a different flag) before a WWD reset. This makes it also possible to distinguish between POR, reset and WWD reset. But I like the event recorder way more and will implement that most likely.